1. Technical Field of the Invention
The present invention relates to a conveying holder for a cylindrical cell being manufactured in an assembling process, which determines the orientation of the cell and conveys the cell while supporting it in an upright state.
2. Description of Related Arts
As the demand for batteries is now increasing sharply, it is desired to produce a great amount of batteries while maintaining their quality level as well as reliability. In a process of manufacturing batteries, unfinished batteries are carried by a known conveyor system from one step to another for filling a cell housing with an electrode assembly, pouring an electrolyte, applying a sealer, closing the cell housing with a sealing member, and so on. In the above mentioned processes, cell housings are held in their upright state by a conveying holder for a series of the steps. Such a conveying holder may be used to hold a cell housing, an in-process cell, or a finished cell product at each step for precise positioning. For simplifying the description and understanding, they are all hereinafter referred to as `cell` in this specification.
One of the known conveying holders for the above described purpose is typically shown in FIG. 6. The conveying holder is particularly designed for holding a common cylindrical cell produced in mass production and consists mainly of two holder shells 1a and 1b which are fabricated by separating a synthetic resin cylinder, of which the inner diameter is slightly smaller than the outer diameter of the cell, into two segments on a plane including the axial center thereof. The two holder shells 1a and 1b are joined in opposite relationship to each other by an O-ring tension spring member 3, which is fitted into holder grooves 2 provided on the outer sides of the shells 1a and 1b, so that there is a small gap 1c between the two holder shells 1a and 1b constituting substantially a tubular assembly. The conveying holder allows the cell to be securely held in an upright state in a holding space between its shells 1a and 1b with the help of an urging force of the tension spring member 3.
In some steps, the cell has to be located in a given direction. For precise positioning, one of the holder shells 1a and 1b of the conveying holder shown in FIG. 6 has a recessed surface 4 provided on an outer side thereof at one end opposite to the opening end through which the cell is inserted. More specifically, the cell may be loaded into the conveying holder with its lead extending from an electrode plate being positioned with respect to the recessed surface 4. In each step of the production, the cell in the conveying holder can automatically be orientated by detection of the recessed surface 4.
Also, a cell positioning conveyor means is proposed for improving the productivity of batteries as shown in FIG. 7. The cell positioning conveyor means includes a cell conveying carrier 8 of cylindrical shape for holding a cell 7 in its upright state which has been loaded from an upper opening of the carrier 8 during the production. The cell conveying carrier 8 has a locator recession 9, similar to the recessed surface 4 shown in FIG. 6, provided on an outer side thereof close to the lower end. The recession 9 is used for positioning a cell 7 loaded into the conveying carrier 8 in its upright state. In action, the conveying carrier 8 holding the cell 7 is conveyed in a forward direction denoted by a bold arrow along a conveyor system 11 while being guided from both sides by a pair of bar-like carrier guides 10.
In the above described conveying process, the conveying carrier 8 is transferred while experiencing a rotating force by a difference in friction between the pair of carrier guides 10. The conveyor system 11 includes a carrier slope 12 fixedly mounted thereon having a moderately tapering surface. While rotating, the conveying carrier 8 runs on the carrier slope 12, until its recession 9 comes into direct contact with a side of the carrier slope 12, whereby the conveying carrier 8 steps down and stands on the conveyor system 11. Since the recession 9 directly engages with the side of the carrier slope 12, the conveying carrier 8 is set in an angular position. This allows the cell 7 in the conveying carrier 8 to be automatically positioned and conveyed further while keeping its position.
It is, however, difficult for the cell conveying holder shown in FIG. 6 to have a true roundness of the cell holding space defined by the inner walls of the two holder shells 1a and 1b. Also, the two holder shells 1a and 1b are urged by the yielding force of the tension spring member 3 in a direction that they come closer to each other. Accordingly, the contacting condition between the cell and the holder shells 1a, 1b may greatly vary depending on a combination of the size of the cell holding space and the diameter of the cell.
Particularly, when the curvature radius of the two holder shells 1a and 1b is greater than that of the cell, the holder shells 1a and 1b come into contact with the cell at only two points in their respective center. If the curvature radius of the two holder shells 1a and 1b is smaller than that of the cell, the holder shells 1a and 1b touch the cell at four points at their respective ends. In the latter case, the direction of the pressing force exerted to the cell by the holder shells 1a and 1b differs from that of the pressing force exerted from the contacting four points between the holder shells 1a, 1b and the cell.
This causes the strength for holding the cell to be largely varied corresponding to variations of the contact points between the holder shells 1a, 1b and the cell and of the difference in the direction between the contact points and the pressing force, even if it is assumed that a variation in the yielding force of the tension spring member 3 is negligible. As it is impossible to stably support the cell, it is hardly attained to produce cells of required properties effectively.
Also, while the tension spring member 3 projects slightly from the outer sides of the holder shells 1a and 1b, the slit-like gap 1c is made between the two holder shells 1a and 1b of substantially semicircular shape in cross section arranged opposite to each other. This, together with the fact that the cells cannot be stably supported, may cause changes in the positions and posture of cells relative to the conveying holder, while the conveying holders supporting the cell in its upright state are slid with or collided against each other on a transfer conveyor in the manufacturing process or on a turn table for temporal storage of unfinished products. Also, due to the projection and the gap, the conveying holder itself may stick or stall in a feeder shoot or between the guides.
The cell positioning conveyor means of FIG. 7 is not capable of always holding the cell 7 stably, since the cell conveying carrier 8 simply has a tubular shape of which inner diameter may not always match the diameter of the cell 7. Besides, the cell conveying carrier 8 is moved forward with its recession 9 being slid with the carrier slope 12 for positioning. It is thus required that the cell conveying carrier 8 is continuously guided by the pair of carrier guides 10 of which frictional coefficients are different from each other for turning movements. In such an arrangement, the conveying carrier 8 often tilts or lifts up during the traveling, causing the forward movement of the cell conveying carrier 8 to be declined in both efficiency and stability.